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Biology of Golden Alga, Prymnesium parvum

What Is Prymnesium parvum?

Golden Alga, Prymnesium parvum
Drawing by Robert G. Howells, TPWD

Algae are primitive plants that are usually aquatic and lack true stems,
roots, and leaves. Prymnesium parvum, the golden alga, is a one cell (microscopic),
flagellated member of the haptophytes. It has two hair-like flagella used
to swim through the water. There is also a shorter stiff hair-like structure
called a haptonema. The haptonema can be used to attach the cell to objects.
The cell has a C-shaped chloroplast that wraps around the middle and is
where the yellow-green color is seen. The nucleus is clear and cannot be
seen under a microscope without adding stains to color it. Often there
are round shapes in the bottom of this alga because the cell can pull inside
and digest bacteria and other algae.

We do not know if this alga is native and not identified before the 1980s
or if it is an invasive species accidentally introduced to North America.
Little is known about the environmental requirements of this alga or what
allows it to gain a competitive edge over other species and bloom. An algal
bloom is an explosive increase in the plant population numbers of one or
several alga species.

What we know about the toxins

The golden alga (P. parvum) releases at least two chemical compounds that
combine with cations (positively charged elements such as magnesium [Mg++]
and calcium [Ca++]) in the water to make toxins. The type of toxin created
is dependent on the water chemistry. Usually there is a combination of
toxins in the water. The toxins cause exposed cells (cells without protective
layers such as on the surface of gills and fins) to fail. Excess water
and waterborne chemicals are allowed inside the cells and eventually inside
organism. These exposed cells either die due to chemicals or break open
due to excess water.

How golden alga uses the toxins

Golden alga can ingest (eat) other cells. Researchers think that the toxins
are used to slow down prey (bacteria and other alga), making it easier
for the golden alga to catch and eat them. In fish, the first damage is
to the exposed skin and gill cells. The outer layer cells are damaged,
then the next cell layer is affected, and so on. Soon the gills are so
badly damaged that they are unable to function, and blood vessels in the
gills leak into the water (hemorrhage). At the same time, the toxins and
other waterborne chemicals are entering into the circulatory system of
the fish, and internal organs are damaged. Bleeding also occurs in exposed
areas like fins. Fish behave as if there is not enough oxygen in the water.
They travel at the top of the water surface or rest on the bottom in edges
and shallow areas.

Unlike toxic red tide blooms on the
coast, golden alga toxins have no apparent lethal effect on non-gill breathing
organisms. Cattle, predators,
scavengers, birds and other animals have been observed drinking water during
a bloom, and many eat the dead fish during on-going golden alga fish kills
with no apparent effects. The golden alga toxins are acid-liable, meaning
they breakdown in acidic conditions, such as in the stomach. Researchers
believe this is why animals are able to drink the water and eat affected
fish without having toxic effects. Also, terrestrial animals have skin
layers to protect them; these same layers protect them from the toxins.
Officials from the Texas Department of State Health Services have stated
that the golden alga is not known to be a human health problem, but people
should not pick up dead, or dying, fish for eating.

Would you like to know more?
The Biology of Golden Alga summarizes what we know about the alga and its toxins.

Where does golden alga fit compared to other single-celled organisms?
The Golden Alga Family Tree gives examples of and information about golden alga and other protists.

What does golden alga look like?
TPWD Golden Alga Images has photos of fish kills, golden algal cells, and short videos of live golden alga. These images may be used for noncommercial/educational purposes as long as TPWD is given credit and other site policies are followed.

Golden Alga Information Card: TPWD has collaborated with the Texas Commission on Environmental Quality and other entities to produce a golden alga information card. Download a PDF from the TCEQ website or request a free hard copy from TPWD at hab@tpwd.texas.gov.